The Supreme Court had ordered a CBI probe in 2015 at a time Mr Chouhan was under intense pressure from rival sections within the party and the opposition Congress that linked a spate of more than 30 deaths to the Vyapam scam.

The long list of accused charged by the CBI on Tuesday, however, only includes 3 officials of the Madhya Pradesh Professional Examination Board (Vyapam), 17 middlemen and "three racketeers" who engineered the scam.

These people ensured that aspirants who paid money to clear the 2013 pre-medical test were seated just behind the assigned 'solver', also enrolled as a candidate who would let the beneficiary copy the answers. There were also reports of imposters writing the examination for candidates for a fee or candidates leaving the answer sheet blank which were written at a much later stage.

A CBI statement said 297 beneficiary and solver candidates and 170 guardians of the candidates had been charge-sheeted. The CBI is also going to file charges against 12 minors in a juvenile court.

There had been complaints of exam fraud earlier too and earlier this year, the Supreme Court had cancelled degrees of over 600 doctors who had obtained admission to the course through fraud between 2008 and 2012. But it was only in 2013 that the fraud developed political overtones. Chief Minister Chouhan, the key target of those attacks, had insisted that he should be credited, and not attacked, for the expose.